System Design Tools

Calculators:

db Power Ratio

This calculation will give you the ratio, in decibels, between two
power values. For example, you can calculate the difference in dB
between two amplifiers with different power output specifications.

Enter any two values and press "Calculate" for the remaining value.

Equation used to calculate the data: dB = 10 * Log (Pout / Pin)

db Voltage Ratio

Voltage A

Voltage B

dB

This calculation will give you the ratio, in decibels, between
two voltages. For example, you can calculate the gain needed to raise
the output level from 0.775 volts to 1.4 volts. You can also use this
to calculate how much attenuation you need if, for instance, you have
a 2.0 volt input level and you need to attenuate it to 0.2 volts to
prevent input overload.

Enter any two values and press "Calculate" for the remaining value.

Equation used to calculate the data:dB = 20 * Log (Vout / Vin)

Amplifier Power Required

Listener distance from source

meters

Desired level at listener distance

dBSPL

Loudspeaker sensitivity rating (1W/1M)

dB

Amplifier headroom

dB

Required Amplifier Power

watts

This calculator provides the required electrical power (power output
from the amplifier) to produce a desired Sound Pressure Level (SPL) at a
given distance, along with an amount of headroom to keep the amplifier(s)
out of clip.

Example: You are designing a system where the farthest listening position
from the loudspeaker is 100 meters, and the desired Sound Pressure Level is
85 dB SPL The loudspeaker chosen for the job has a sensitivity rating of 95
dB. With the minimum recommended amplifier headroom of 3 dB, then you need
to choose an amplifier that can supply at least 1,995 watts to the
loudspeaker.

Inverse Square Law

This calculation will give you the amount of attenuation, in decibels, you can
expect with a change in receiver distance, in a free field (outdoors).

For example if you were standing 20 feet from a loudspeaker, and were to move
to 40 feet away from that loudspeaker, you would expect to see a drop in level of
6 dB. Sound that is radiated from a point source drops in level at 6 dB per
doubling of distance.

Ohm's Law / Watt's Law

Ohm's Law states the relationship between current, voltage and resistance.
Watt's Law states the relationships of power to current, voltage and resistance.

Enter any two known values and press "Calculate" to solve for the others.

Equations used to calculate the data:V = IRP = VI

Where:I = currentP = powerR = resistanceV = voltage

"Constant Voltage" Transformer Delivered Power

V new

volts

V rated

volts

P rated

watts

P actual

watts

Many people don't realize that a transformer labeled for use with a specific
voltage will work just as well at other voltages. This calculator provides power
delivered from a transformer tap when driven with other than the rated voltage.

Example: You are installing a distributed system with very long lines. To
overcome line loss, you select a 140 volt system. Which transformer tap will
feed 10 watts to a loudspeaker with a 70V transformer?